We are developing the technology necessary to determine the enzymic contents of individual zymogen granules. We apply micromanipulation techniques and a fluorometric method scaled down to final volumes in the picoliter range to measure pancreatic secretory proteins (amylase, chymotrypsinogen, trypsinogen, lipase and procarboxypeptidase A) in individual pancreatic exocrine cells. We will evaluate the use of electron probe microanalysis of zinc to determine the distribution of carboxypeptidase among zymogen granules. Results of this study will provide for the first time the detailed content of secretory proteins in individual mammalian cells and individual cellular organelles. The methods developed should have wide application in cell physiology.